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2. B.Z. Malkin, in: A.A. Kaplyanskii, R.M. Macfarlane (Eds.), Modern Problems in Condensed Matter Physics, vol. 21, North-Holland Physics Publishing, 1987, p. 13.
3. Hyperfine structure in optical spectra of LiYF4-Ho
4. R.L. Cone, R.S. Meltzer, in: A.A. Kaplyanskii, R.M. Macfarlane (Eds.), Modern Problems in Condensed Matter Physics, vol. 21, North-Holland Physics Publishing, 1987, p. 481.
5. Isotope structure in optical spectra of LiYF_{4}:Ho^{3+}